The Rio Pereque-Açu is a coastal river system located in the state of Rio de Janeiro, Brazil, draining through the Atlantic Forest — one of the world's most biodiverse and threatened biomes. The river basin supports a rich and largely endemic ichthyofauna, making it a fascinating destination for anglers and naturalists alike. Its coastal drainage character means the river flows relatively short distances from forested highlands to the sea, creating a mosaic of habitats ranging from shaded headwater streams to broader lowland reaches. The basin has been the subject of scientific fish surveys that have documented 23 native species across 10 families, reflecting the ecological richness typical of Atlantic Forest river systems.